Fall soil testing can make a big difference to next year's crop

Fall soil testing can make a big difference to next year’s crop

Now is an ideal time to soil test to get accurate information on which to base fertility decisions for the 2022 growing season. Warren Ward, CCC Agronomy Specialist at Springside, SK, says that if fall soil testing, you should test as late as possible to give an accurate assessment of what the nutrient levels will be in the spring. Soil testing should be done as close to freeze up as possible when the soil is cool (below 10C). 

“Waiting until soil is cool helps reduce nutrient content changes due to microbial activity that may occur prior to seeding next spring. If you band fertilizer in the fall, it can give you a good idea of the rates you need to apply. Testing in the spring provides the most accurate assessment, but it can leave very little time for planning.”

Ward emphasizes that it’s especially important to soil test after the growing season we’ve just experienced. In addition to the regular benefits of soil testing for nutrient planning, poor crop growth in 2021 has led to higher than normal residual nutrient levels in the soil for many farms. The best way to measure what your residual nutrient levels are in the soil is through soil testing.

“Nitrogen is one that in many cases has higher than normal carryover because it was so dry. To a large extent, if it wasn’t used by the plants it is still just sitting there. Testing is relatively cheap compared to the fertilizer bill, so you might as well test for soil nutrients. Otherwise it’s just a guessing game and with today’s fertilizer prices, that’s not the wisest strategy.”

Ward recommends that growers understand what they want to get out of the soil test. Is it a general aggregate field sample analysis? If you want to account for more variability and different zones within a field, you should consult field maps and sample throughout the field at the upper slope, mid slope, and lower slope. Having variable rate capabilities will also make a difference in how you soil test. 

The results will help growers decide what to crop next year, as well as identify target yields, nutrients required and the amount and types of fertilizer to apply.

Proper soil sampling is necessary for meaningful soil test results. A sampling error in the field is usually much greater than the analytical error in the lab. Ensure soil samples accurately reflect the overall field, or zones within the fields for more intensive management.

Nutrient content in soil varies over years, between fields and there is even inherent nutrient spatial variability within fields that appear uniform. Although soil testing is just an estimation, it can help give reasonable guidelines for profitable fertilizer application as part of the right rate considerations when following the 4R nutrient stewardship practices.

More information on soil testing methods
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